The Effect of Piston Bowl and Spray Configuration on Diesel Combustion and Emissions

2011 ◽  
Author(s):  
Bassem H. Ramadan ◽  
Charles L. Gray ◽  
Fakhri J. Hamady ◽  
Cody Squibb ◽  
Harold J. Schock
Keyword(s):  
Spray Angle ◽  
Diesel Combustion ◽  
Cylinder Pressure ◽  
Fuel Injector ◽  
Fuel Injectors ◽  
Rich Mixture ◽  
Piston Bowl ◽  
Air Mixing ◽  
Fuel Mass Fraction ◽  
Insight Into

A numerical and experimental study of the effect of piston bowl and spray configuration on diesel combustion and emissions has been conducted. The objective of this study is to gain better understanding of the effect of the piston bowl shape and fuel injector configuration on fuel-air mixing, combustion, and emissions in a diesel engine. Ideally, a uniform fuel-air mixture in the cylinder is desired to prevent the formation of regions containing a rich mixture, where soot is usually formed, and regions of lean mixtures, where nitrogen oxides are formed. Different piston bowl shapes and fuel injectors (number of nozzles, spray angle) have been considered and simulated using computational fluid dynamics and experiments. CFD calculations of fuel mass fraction, and measurements of cylinder pressure and emissions species are included. The results show that computer simulations coupled with experiments provide insight into the interactions between fluid flow, fuel-air mixing, combustion, and emissions.

Numerical Prediction of Fluid Flow and Diesel Combustion in a Pre-Chamber and Main Chamber

2005 ◽  
Author(s):  
Bassem H. Ramadan ◽  
Prashant Ahire
Keyword(s):  
Fluid Flow ◽  
Diesel Combustion ◽  
Cylinder Pressure ◽  
Main Chamber ◽  
Ic Engine ◽  
Piston Bowl ◽  
Air Mixing ◽  
Model Fluid ◽  
Computational Fluid Dynamics Cfd ◽  
Turbulence Generation

In this study computational fluid dynamics (CFD) was used to model fluid flow and diesel combustion in an IC engine that uses a pre-chamber and a main-chamber. The pre-chamber is located in the cylinder head and a bowl in the piston serves as the main chamber. The study considers the effect of diesel combustion in the pre-chamber on turbulence generation and hence fuel-air mixing and combustion in the piston-bowl. Diesel fuel was injected directly into the pre-chamber and the piston bowl at different times. In order to better determine the effect of pre-chamber combustion on the main chamber combustion, various pre-chamber injection timings were considered. The results show that pre-chamber combustion caused the average cylinder pressure to increase by up to 20% in some cases.

The Effect of Liquid-Fuel Preparation on Gas Turbine Emissions

2006 ◽  
Author(s):  
Sosuke Nakamura ◽  
Vince McDonell ◽  
Scott Samuelsen
Keyword(s):  
Gas Turbine ◽  
Liquid Fuel ◽  
Cylindrical Tube ◽  
Spray Angle ◽  
Preparation Process ◽  
Fuel Injector ◽  
Secondary Importance ◽  
Turbine Engine ◽  
Performance And Emissions ◽  
Air Mixing

The emissions of liquid-fuel fired gas turbine engines are strongly affected by the fuel preparation process that includes atomization, evaporation and mixing. In the present paper, the effects of fuel atomization and evaporation on emissions from an industrial gas turbine engine were investigated. In the engine studied, the fuel injector consists of a co-axial plain jet airblast atomizer and a premixer, which consists of a cylindrical tube with four mixing holes and swirler slits. The goal of this device is to establish a fully vaporized, homogeneous fuel/air mixture for introduction into the combustion chamber and the reaction zone. In the present study, experiments were conducted at atmospheric pressure and room temperature as well as at actual engine conditions (0.34MPa, 740K) both with and without the premixer. Measurements included visualization, droplet size and velocity. By conducting tests with and without the premixing section, the effect of the mixing holes and swirler slit design on atomization and evaporation was isolated. The results were also compared with engine data and the relationship between premixer performance and emissions was evaluated. By comparing the results of tests over a range of pressures, the viability of two scaling methods was evaluated with the conclusion that spray angle correlates with fuel to atomizing air momentum ratio. For the injector studied, however, the conditions resulting in superior atomization and vaporization did not translate into superior emissions performance. This suggests that, while atomization and the evaporation of the fuel are important in the fuel preparation process, they are of secondary importance to the fuel/air mixing prior to, and in the early stages of the reaction, in governing emissions.

The Effect of Liquid-Fuel Preparation on Gas Turbine Emissions

2008 ◽  
Vol 130 (2) ◽  
Author(s):  
Sosuke Nakamura ◽  
Vince McDonell ◽  
Scott Samuelsen
Keyword(s):  
Gas Turbine ◽  
Liquid Fuel ◽  
Cylindrical Tube ◽  
Spray Angle ◽  
Preparation Process ◽  
Fuel Injector ◽  
Secondary Importance ◽  
Turbine Engine ◽  
Performance And Emissions ◽  
Air Mixing

The emissions of liquid-fuel fired gas turbine engines are strongly affected by the fuel preparation process that includes atomization, evaporation, and mixing. In the present paper, the effects of fuel atomization and evaporation on emissions from an industrial gas turbine engine were investigated. In the engine studied, the fuel injector consists of a coaxial plain jet airblast atomizer and a premixer which consists of a cylindrical tube with four mixing holes and swirler slits. The goal of this device is to establish a fully vaporized, homogeneous fuel/air mixture for introduction into the combustion chamber and the reaction zone. In the present study, experiments were conducted at atmospheric pressure and room temperature as well as at actual engine conditions (0.34MPa, 740K) both with and without the premixer. Measurements included visualization, droplet size, and velocity. By conducting tests with and without the premixing section, the effect of the mixing holes and swirler slit design on atomization and evaporation was isolated. The results were also compared with engine data and the relationship between premixer performance and emissions was evaluated. By comparing the results of tests over a range of pressures, the viability of two scaling methods was evaluated with the conclusion that spray angle correlates with fuel to atomizing air momentum ratio. For the injector studied, however, the conditions resulting in superior atomization and vaporization did not translate into superior emissions performance. This suggests that, while atomization and the evaporation of the fuel are important in the fuel preparation process, they are of secondary importance to the fuel/air mixing prior to, and in the early stages of the reaction in, governing emissions.

A Multi-Zone Reaction-Based Diesel Combustion Model for Model-Based Control

2017 ◽  
Author(s):  
Yifan Men ◽  
Guoming G. Zhu
Keyword(s):  
Diesel Engine ◽  
Reaction Zone ◽  
Liquid Fuel ◽  
Spherical Shape ◽  
Combustion Model ◽  
Reactive System ◽  
Zone Model ◽  
Diesel Combustion ◽  
Cylinder Pressure ◽  
Air Mixing

A physics-based control-oriented combustion model is developed to accurately predict in-cylinder pressure and temperature of a diesel engine. The model is under the assumption that the combustion chamber consists of three zones: a liquid fuel zone, a reaction zone, and an unmixed zone. These zones are formulated to account for three key events in diesel combustion: fuel evaporation, chemical reaction, and fuel-air mixing, respectively. The liquid fuel zone is assumed to be of spherical shape. The evaporation of fuel is governed by Fick’s first law of diffusion. The reaction zone is modeled as a reactive system consisting of six species and two reaction steps. The burn rate is calculated based on species concentrations and reaction zone temperature. The unmixed zone contains only air and inert gas. The results of simulations are compared to the test data from a GM 6.7 L 8-cylinder Duramax diesel engine. The multi-zone model is shown to be capable of predicting in-cylinder pressure accurately with more degree of freedoms, compared to the singlezone reaction-based model.

scholarly journals Fuel Spray Characteristics of Gas Turbine Fuel Injectors at Cold Start Conditions

1995 ◽  
Author(s):  
Theodore R. Koblish ◽  
Theodore G. Fox ◽  
Subhash G. Patel ◽  
Jamil R. Siddiqui
Keyword(s):  
Droplet Size ◽  
Droplet Diameter ◽  
Spray Angle ◽  
Fuel Spray ◽  
Jet Engines ◽  
Fuel Injector ◽  
Fuel Type ◽  
Fuel Injectors ◽  
Fuel Flow ◽  
The Military

Engine starting at extremes of cold ambient and fuel temperatures are a concern to both military and commercial operators of jet engines, but the military in particular needs the capability to quick start under very cold conditions. The ongoing worldwide conversion to JP8 fuel is compromising this ability for older engines developed for use on wide-cut JP4 fuel. The greatly reduced volatility and increased viscosity of JP8 fuel significantly impacts fuel spray angle and droplet size at start conditions resulting in over-long and aborted starts in cold climates. A program was carried out by Pratt & Whitney and Textron Fuel Systems to investigate and improve the spray qualities of a dual orifice pressure atomizing fuel injector of a commonly used military jet engine in the start to low power range. The primary fuel injector portion was modified to produce a finer droplet size and wider spray angle. A hybrid design with an aerating secondary was also tested. Droplet diameter and spray angles were measured to −40°F (−40°C) temperatures. Variations in fuel flow rate and fuel type were also investigated. It was found that cold fuel had an adverse effect on spray qualities for the all pressure atomizing nozzles, but the hybrid injector was less affected and produced superior sprays at all conditions on the primary portion. Improvements in the all pressure atomizing design resulted in lesser but still significant benefits.

Development of Flashback Resistant Low-Emission Micro-Mixing Fuel Injector for 100% Hydrogen and Syngas Fuels

2009 ◽  
Author(s):  
Howard Lee ◽  
Steve Hernandez ◽  
Vincent McDonell ◽  
Erlendur Steinthorsson ◽  
Adel Mansour ◽  
...  
Keyword(s):  
Axial Flow ◽  
Elevated Pressure ◽  
Small Scale ◽  
Fuel Injector ◽  
Fuel Injectors ◽  
Lean Blowout ◽  
Conflicting Demands ◽  
Fuel Flexibility ◽  
Low Emission ◽  
Air Mixing

The present work extends previous efforts using “micro-mixing” fuel injectors operating on hydrogen fuel to elevated pressure and temperature and includes initial evaluation of a second injector concept. A micro-mixing fuel injector consists of multiple, small and closely spaced mixing cups, within which fuel and air mix rapidly at a small scale. The micro-mixing injection strategy offers inherent flexibility for the accommodation of staging, dilution, and fuel flexibility, and the manufacturing technology employed for building the cups affords great flexibility to address the conflicting demands of superior fuel-air mixing and flash-back avoidance. In the present work, both radial and axial flow micromixing concepts are investigated using experiments and computational fluid dynamics. The hydrogen/air reaction structure is captured using OH* chemiluminescence at 308 nm, recorded using a 16-bit thermoelectrically cooled ICCD with a UV sensitive phosphor. Instantaneous images are used to assess flashback tendencies at pressures up to 8 atm for reaction temperatures approaching 2000 K. Emissions are measured at the exit of the combustor liner using EPA certified methodologies. The results demonstrate that both concepts can produce low NOx emissions while remaining robust relative to flashback and lean blowout. The radial concepts offer superior emissions performance, while the axial concepts offer superior flashback tendencies. Based on the results obtained to date, the micro-mixing approach appears promising relative to achieving flashback free operation with low emissions at pressures up to 8 atm while maximizing scalability and fuel flexibility.

The Civic: A Concept in Vortex Induced Combustion for the Solar Gemini 10 kW Gas Turbine

1981 ◽  
Vol 103 (1) ◽  
pp. 34-42 ◽  
Author(s):  
J. R. Shekleton
Keyword(s):  
Gas Turbine ◽  
Diffusion Flames ◽  
Reynolds Numbers ◽  
Flame Stabilization ◽  
Fuel Injector ◽  
Combustion Chambers ◽  
Turbine Generator ◽  
Fuel Injectors ◽  
Swirl Flame ◽  
Combustion Processes

The Radial Engine Division of Solar Turbines International, an Operating Group of International Harvester, under contract to the U.S. Army Mobility Equipment Research & Development Command, developed and qualified a 10 kW gas turbine generator set. The very small size of the gas turbine created problems and, in the combustor, novel solutions were necessary. Differing types of fuel injectors, combustion chambers, and flame stabilizing methods were investigated. The arrangement chosen had a rotating cup fuel injector, in a can combustor, with conventional swirl flame stabilization but was devoid of the usual jet stirred recirculation. The use of centrifugal force to control combustion conferred substantial benefit (Rayleigh Instability Criteria). Three types of combustion processes were identified: stratified and unstratified charge (diffusion flames) and pre-mix. Emphasis is placed on five nondimensional groups (Richardson, Bagnold, Damko¨hler, Mach, and Reynolds numbers) for the better control of these combustion processes.

A Computational Investigation of Piston Bowl Geometry for a Large Bore Two-Cycle Diesel Engine

2011 ◽  
Author(s):  
Jonathan Dolak ◽  
Deep Bandyopadhyay
Keyword(s):  
Diesel Engine ◽  
Fuel Consumption ◽  
Simulation Software ◽  
Spray Angle ◽  
Tier 2 ◽  
Piston Bowl ◽  
Cylinder Test ◽  
Advanced Combustion ◽  
Combustion Simulation ◽  
Reduce Emissions

The objective of this research was to optimize an Electro-Motive Diesel (EMD) large-bore, two-cycle diesel engine (710 cubic inches of displacement per cylinder) at high load to minimize soot, nitrogen oxide (NOx) and fuel consumption. The variables considered were the number of spray-hole nozzles per injector, including spray angle and piston bowl geometry, for a range of injection pressures. Analytical simulations were conducted for a calibrated EMD 710 Tier 2 engine and a few of the top-performing cases were studied in detail. CONVERGE™, a commercially available, advanced combustion simulation software was used in this analysis. A surface deforming tool, Sculptor®, was used to obtain various piston bowl geometries. MiniTab® was utilized for statistical analysis. Results show that optimal combinations of injection variables and piston bowl shape exist to simultaneously reduce emissions and fuel consumption compared to Tier 2 EMD 710 engines. These configurations will be further tested in a single-cylinder test cell and presented later. This investigation shows the importance of bowl geometry and spray targeting on emissions and fuel consumption for large-bore, two-stroke engines with high power density.

scholarly journals Characterization of a Novel Porous Injector for Multi-Lean Direct Injection (M-LDI) Combustor

2017 ◽  
Author(s):  
Jianing Li ◽  
Umesh Bhayaraju ◽  
San-Mou Jeng
Keyword(s):  
Air Temperature ◽  
Mass Fraction ◽  
Direct Injection ◽  
Flame Temperature ◽  
Gaseous Fuel ◽  
Nox Emissions ◽  
Fuel Injector ◽  
Porous Tube ◽  
Lean Direct Injection ◽  
Air Mixing

A generic novel injector was designed for multi-Lean Direct Injection (M-LDI) combustors. One of the drawbacks of the conventional pressure swirl and prefilming type airblast atomizers is the difficulty of obtaining a uniform symmetric spray under all operating conditions. Micro-channels are needed inside the injector for uniformly distributing the fuel. The problem of non-uniformity is magnified in smaller sized injectors. The non-uniform liquid sheet causes local fuel rich/lean zones leading to higher NOx emissions. To overcome these problems, a novel fuel injector was designed to improve the fuel delivery to the injector by using a porous stainless steel material with 30 μm porosity. The porous tube also acts as a prefilming surface. Liquid and gaseous fuels can be injected through the injector. In the present study, gaseous fuel was injected to investigate injector fuel-air mixing performance. The gaseous fuel was injected through a porous tube between two radial-radial swirling air streams to facilitate fuel-air mixing. The advantage of this injector is that it increases the contact surface area between the fuel-air at the fuel injection point. The increased contact area enhances fuel-air mixing. Fuel-air mixing and combustion studies were carried out for both gaseous and liquid fuel. Flame visualization, and emissions measurements were carried out inside the exit of the combustor. The measurements were carried out at atmospheric conditions under fuel lean conditions. Natural gas was used as a fuel in these experiments. Fuel-air mixing studies were carried out at different equivalence ratios with and without confinement. The mass fraction distributions were measured at different downstream locations from the injector exit. Flame characterization was carried out by chemiluminescence at different equivalence ratios and inlet air temperatures. Symmetry of the flame, flame length and heat release distribution were analyzed from the flame images. The effects of inlet air temperature and combustion flame temperature on emissions was studied. Emissions were corrected to 15% O2 concentration. NOx emissions increase with inlet air temperature and flame temperature. Effect of flame temperature on NOx concentration is more significant than effect of inlet air temperature. Fuel-air mixing profile was used to obtain mass fraction Probability Density Function (pdf). The pdfs were used for simulations in Chemkin Pro. The measured emissions concentrations at the exit of the injector was compared with simulations. In Chemkin model, a network model with several PSRs (perfectly stirred reactor) were utilized, followed by a mixer and a PFR (plug flow reactor). The comparison between the simulations and the experimental results was investigated.

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